The following description relates to a fluid dispensing system, and in particular, a fluid dispensing system having a nozzle heater.
Fluid dispensing systems are used in many industries to, for example, dispense an adhesive or other thermoplastic material onto an item. One such use is in the manufacture of disposable diapers where an adhesive may be dispensed onto an elastic strand for securing the strand to the body of the diaper. Other uses include the application of an adhesive onto a packaging container or carton to seal the carton flaps.
These systems often operate at high speeds to maintain acceptable manufacturing outputs. And, in order to maintain high output, the dispensing nozzles must be maintained at a dispensing temperature to assure that the dispensed material is at a desired temperature.
Current adhesive fiberizing technology uses a combination of actively heated service blocks and air heat exchangers in an attempt to assure the extruded adhesive is at the desired application temperature as it exits the applicator nozzle. The maintenance of nozzle temperature is accomplished via conduction of heat from the glue applicator service block, through the valve module to the nozzle assembly. The air heat exchanger is incorporated into the applicator assembly to further assure nozzle temperatures are maintained by flowing superheated air through the nozzles as the adhesive is applied.
However, reliance upon thermal conduction from the applicator service block, through the module to the nozzle and the use of superheated air is inadequate to maintain the nozzle at the desired application temperature. This shortfall becomes more amplified as the volume of air through the nozzles is increased. The result is that temperatures in excess of 100° F. (38° C.) below the desired set temperature have been observed at the exit point of the nozzle.
This decrease in temperature causes the adhesive to cool as it flows through the valve module and nozzle assemblies. The reduction in adhesive temperatures causes thermal adhesives to thicken, making it more difficult for the adhesives to flow through the nozzle's small passageways. This results in restricted flow through the nozzles, degraded adhesive application patterns and, potentially, plugging of the nozzles, especially after periods of applicator inactivity when the air is flowing through the nozzles and the adhesive has additional time to cool because it is stagnant inside the valve module and nozzle for a protracted time period.
Accordingly, there is a need for a dispensing system that is configured to maintain the temperature of the nozzles, and thus the adhesive, at a minimum desired temperature.